How to download the Songs of Innocence album by U2 for free on iPhone and iPad

U2 took the stage today at Apple's iPhone event and along with a free performance, also announced that their new album, Songs of Innocence, would be made available for free to all iPhone and iPad owners via iTunes. The biggest question we're getting bombarded with now is how exactly you go about downloading it. As it turns out, you've just got to know where to look.